In hemodialysis and other blood processing treatment, the priming of blood lines leading to a dialyzer from the patient is currently a labor intensive procedure, tying up technicians and nurses from more productive activities.
The blood lines and priming sets are typically provided in xe2x80x9cdryxe2x80x9d form, while dialyzers are sometimes dry or wet-packed. If reused, dialyzers are wet on each use after the initial use. Wet and dry dialyzers require different priming procedures.
During the priming, the filters, found in chambers of the venous blood sets are difficult to debubble as the sets are primed with saline or other priming solution, because in typical procedures the priming solution comes from above into the venous chamber. Bubbles may remain trapped next to and under the filter of the venous chamber. In current practice, the venous chamber generally has to be turned upside down during part of the priming procedure, to cause the bubbles to pass upwardly through a portion of the venous set and, accordingly, out of the set so that it becomes filled with priming solution in bubble-free manner. During priming, the patient end of the venous set is conventionally placed in an unsterile bucket or drain to catch excess priming or rinse fluid as it drains out of the set. This allows the risk of contamination if the connector at the end of the venous set falls into or otherwise touches the bucket or drain.
At another stage of the conventional priming procedure, the arterial and venous blood lines may be typically connected together via a xe2x80x9crecirculation interconnectorxe2x80x9d for the recirculation stage of the priming procedure. This recirculation xe2x80x9cdialysesxe2x80x9d out through a connected blood processing unit (dialyzer) contaminants left over from the manufacturing or any reuse process that has preceded the priming.
If the recirculation interconnector is not sterile, another chance for touch contamination of the patient connectors of the respective arterial and venous sets occurs as the respective sets are connected together during the priming procedure by means of such a recirculation interconnector.
This problem is intensified by the fact that the respective connectors of the arterial and venous sets are wet at the time they are conventionally connected with the recirculation interconnector, making contamination by this reconnection a greater likelihood.
In the case of a wet dialyzer (or a re-used dialyzer), the arterial bloodline typically is not connected to the dialyzer until after priming. This prevents air from being introduced into the dialyzer, which will happen in a conventional priming procedure.
In conventional priming techniques, the arterial patient connector tube and adjacent tubing may not be adequately rinsed during the priming procedure.
Cobe Laboratories sells the Centry III dialysis machine in which the blood sets may be automatically primed. However, special equipment is required for this automatic priming process. For example, during the process, the blood pump runs backwards for a period of time, thus requiring a blood pump that can pump in either direction. Hence, the Cobe priming process cannot be used with an ordinary dialysis machine to automatically prime arterial and venous sets connected to a dialyzer, if such conventional dialysis equipment has a blood pump that pumps in only one direction. See also Heath et al. U.S. Pat. No. 4,770,787.
Nikkiso Japan has a priming procedure that similarly requires a pump that can be reversed and additionally requires a fluid flow measuring device and timing device to make it automatic.
By this invention, the above problems and inconvenient characteristics can be eliminated or greatly reduced as problems, this being accomplished by a novel method for priming blood sets, which are for use with dialyzers or for use in other blood processing systems.
A partial list of the advantages which can be achieved by this invention is as follows:
1. All flow through prime and blood pathway components of the blood processing system can be connected prior to priming. Particularly, the arterial and venous set patient connectors can be pre-connected in the factory via an interconnector, and sterilized in that form. Thus, the risk of contamination by connector disconnection and later connection to the interconnector is eliminated. Preferably, the interconnector is long enough to receive two fistula needles (or equivalent connectors thereto such as blunt needles or other blood access devices), one extending from each of the patient connectors. Thus, the fistula needles may optionally be in place on the respective sets as received by the user, sterile, and ready for use. Also, the reused system may be reprimed without disconnection of the arterial bloodline from the dialyzer. Also, a dialyzer may be pre-attached to the blood sets, which with pre-attached fistula needles would form a complete extracorporeal circuit.
2. The priming procedure fills the venous chamber and any other filter-carrying chamber of the sets with substantially spontaneous or automatic debubbling, without the need for inverting the chamber or the like.
3. The priming procedure can move from a rinsing mode to a recirculation mode by simply changing the rate of flow of priming solution into the system or the pumping rate through the system.
4. All blood and prime flow pathway segments of the arterial and venous bloodlines are effectively rinsed.
5. No part of the blood pathway comes close to any drain bucket or the like, so that the risk of contamination of the blood pathway from this source is greatly reduced.
6. No special machinery is needed. Particularly, mechanical pumping in two sequential directions through the set is not required.
Thus, a blood processing system is provided in which the priming technique is greatly simplified, with a substantial reduction in both the retention of undesirable air bubbles and in the risk of contamination.
In accordance with this invention, a tubular blood set is provided which comprises a length of blood tubing, having a branch connection with drain tubing that can lead to a fluid drain or receptacle. Typically, this drain tubing is free of permanent physical connection to the drain receptacle, and can be closed off when its use in priming is no longer needed by clamping.
Preferably, this invention relates to a blood processing system which comprises a blood processing unit such as a dialyzer and connected, tubular, arterial and venous sets for blood flow between the unit and the patient. However the blood sets may be primed while connected together without the blood processing unit, and the blood processing unit is then inserted between the sets after priming. Thus priming of the whole system can take place without passing air through a wet, reused dialyzer, thus avoiding trapped bubbles therein.
In its initial configuration for priming, prior to connection with the arteriovenous system of the patient, each of the arterial and venous sets comprises a patient connector at the ends of the sets opposed to set ends that connect (during or after priming) with the blood processing unit. Each of these patient connectors may preferably carry a fistula needle or another access device with the bloodstream of the patient, with the two patient connectors or the access devices being connected by an interconnector, causing them to be in flow relationship which each other. The interconnector may enclose the respective fistula needles or other access devices or said patient connectors. By this, the advantages described above can be achieved.
Further by this invention, a method is provided of priming the above-described blood processing system by the following steps incorporated in a priming process: (1) one passes priming solution in a first direction of flow through at least one of the sets, and preferably portions of both sets including the interconnector, to cause the priming solution to enter an in-line, preferably filter-carrying chamber, carried by the one set, in a flow direction that is retrograde to the normal direction of blood flow through the chamber. One simultaneously removes air or prime from the system through a port that is not a patient connector. (2) In another step, which preferably may be simultaneous with, or alternatively previous or subsequent to the above described step, one passes priming solution in a second, reverse direction of flow to the first direction, preferably through the blood processing unit and connected sets, or the connected sets without the blood processing unit, while continuing to vent air or priming solution from the system through the port.
The priming volume of a tube set and dialyzer is typically 250 cc. or less. Typically, at least 500 ml. of saline is introduced to the set. Thus, about 250 cc. is used in priming, (i.e. only air displacement). The additional 250 cc. of saline is used in overflow rinsing (also called flushing). Thus, priming, or priming and rinsing, of the system is completed.
The second, reverse direction of flow is preferably the normal direction of flow that blood will take through the set during the blood processing procedure, preferably with the aid of a pump rotating in its normal, blood processing direction. Thus, flow may proceed through the set or sets in two directions from the point where the priming solution is introduced, to the air and prime venting port. When the two-direction flow is simultaneous and flow is assisted in the second direction by a pump, priming time can be shortened.
The blood processing unit may be typically be a hemodialyzer, respectively connected at the dialyzer arterial and venous blood ports to the arterial and venous sets, preferably with said dialyzer port positioned below the dialyzer""s venous port.
Also, after the air has been removed by priming, it is preferred to connect in the dialyzer if not already connected, and to pass priming solution through the blood processing system and then out of the port, to flush the system. By this procedure, it becomes possible to prime, flush, and xe2x80x9crecirculatexe2x80x9d all portions of the sets, as well as the blood processing unit (dialyzer) as a second phase of the priming process prior to inserting blood into the system for the processing thereof.